Like trees, shrub roots grow both horizontally and vertically. All shrubs require a healthy root system to grow and flourish, but some species depend on deep roots while others thrive with a shallow, lateral root system. Such shrubs make appropriate planting choices in landscapes where deep roots can be harmful, such as near septic pipes or fields. When choosing shrubs with lateral roots, choose species with cultural requirements that best match the conditions in your landscape.
Several maple (Acer spp.) shrubs have lateral roots. Cultivars of the Norway maple (A. planatoides) have shallow root systems. The Stand Fast maple grows very slowly from 1 to 3 feet tall with a narrow, foot-wide spread. It has an upright form and small, deep-green foliage that grow in clusters at the end of its branches. Stand Fast maples are hardy in U.S. Department of Agriculture plant hardiness zones 4 to 7 and grow well in sun to partial shade and moist, well-drained soil. The Tartarian maple (A. tartaricum) is hardy to zone 3 and transplants easily. It grows from 15 to 20 feet tall and has trilobed, dark-green foliage that turns yellow and red in early fall. Tartarian maples prefer full sun to light shade and well-drained, cool soil.
Several alder (Alnus spp.) shrubs have shallow roots. The tag alder (Alnus serrulata) grows as a large shrub or small tree from 15 to 20 feet tall. The tag alder is hardy in zones 5 to 9 and tolerates sun to partial shade and a range of soils. It produces yellow spring catkins and bird-attracting, long-lasting winter fruits. The speckled alder (A. incana) also grows as a large shrub or small tree and reaches heights to 25 feet. It produces reddish catkins in spring followed by dry fruits. Speckled alder prefers full sun to light shade and moist to wet soils.
Dogwood shrubs (Cornus spp.) have shallow roots. The Tartarian dogwood (C. alba) grows to 10 feet tall with a similar spread and is hardy in zones 3 to 7. It has loose, upright branches with dark-green foliage and produces yellow-white spring blossoms. The bloodtwig dogwood (C. sanguinea) grows to 15 feet tall with an equal spread. Hardy in zones 4 to 7, this shrub is named for its bright-red stems. It blooms with malodorous white flowers in early summer. The red osier dogwood (C. sericea) grows to 9 feet tall with a slightly wider spread and is hard in zones 2 to 7. It has dark green foliage that turns purple to red in fall. Dogwoods are deciduous and grow well in sun to partial shade and a range of soils.
Several other shrubs have lateral roots, such as the gumball sweetgum (Liquidambar styraciflua "Gumball"). This shrub grows to 15 feet tall with an 8- to 10-foot spread. It has deciduous foliage that turns purple, red, orange and yellow in fall. Gumball sweetgums are hardy in zones 6 to 9 and grow best in full sun and moist, well-drained soil.
The American hornbeam (C. caroliniana) grows as a large shrub or small tree with shallow roots. This deciduous plant is hardy in zones 3 to 9 and grows slowly to 30 feet tall with a similar spread. American hornbeams prefer sun to partial shade and moist to wet soil.
- Colorado State University Extension; Fall and Winter Watering
- Iowa State University Extension; Sidewalks and Trees; Sherry Rindels; March 31, 1995
- University of Wisconsin at Green Bay: Trees of Wisconsin Alnus Incana
- University of Connecticut; Plant Database of Trees, Shrubs and Vines; Mark H. Brand
- North Carolina State University; Shrubs; Erv Evans